Database Engines/Servers Software

HSQLDB is a relational database engine written in Java, with a JDBC driver, conforming to ANSI SQL:2008. A small, fast, multithreaded engine and server with memory and disk tables, LOBs, transaction isolation, multiversion concurrency and ACID.

The Lemur Project develops search engines, browser toolbars, text analysis tools, and data resources that support research and development of information retrieval and text mining software, including the Indri search engine and ClueWeb09 dataset.

Joseki: The Jena RDF Server.
Joseki is a server for publishing RDF models on the web. Models have URLs and they can be access by HTTP GET. Joseki is part of the Jena RDF framework.
Jena has moved to Apache: http://jena.apache.org/
Joseki is replaced by Apache Jena Fuseki.

See http://www.cubrid.org/cluster. CUBRID Cluster is an open source clustered DBMS for high scalability including global schema, distributed partition and load balancing features. It is a spin-off project from CUBRID project and supported by NHN.

OpenEMed is a distributed healthcare and medical information framework based on open standards including those of HL7 and the healthcare taskforce of the OMG. These standards include identity management, observation access, access, and terminology.

Data Evolution for Java. Finch is a Data Transformation System based on JDBC and other Java blessed specifications. Finch is based on a component task architecture allowing users to create complex data manipulation jobs.

Ridiculously simple, Prevayler provides transparent ACID persistence and replication for plain old Java objects. It is literally several thousand times faster than using a relational database through JDBC.

SiebenGeisslein is a platform for orthogonal persistent applications. Its main components are an object store, an application server and an IDE. The features include multi-user support, crash-recovery, hot-deployments and transparent object evolution.

Full featured AJAX web based reporting system. Written in Java / JSP. Web based reports are dynamically generated from JDBC result sets. Connects to any JDBC compliant database, most drivers already included. The Apache Derby database is embeded.

Gemello is a relational database written in pure Java. Its design is aimed at teaching. If you're searching for a fast relational engine, Gemello won't be a good choice. Is's rather a good and simple example of relational database implementation.

OpenRolap: an implementation of OLAP in a relational database. Conceptually simple, the current version is in MySQL, with a Java API. The API aims to avoid complex MDX-type language, instead to use a simple "filter path" structure.

The iChilli mobile J2EE platform provides a J2EE compliant runtime environment for both server and mobile platforms, such as J2ME, MIDP or other CLDC based devices. For example iChilli runs on the PersonalJava enabled Sharp Zaurus and Compaq's iPAQ.